The transmission of data over a data network typically involves sending messages between application programs (“applications”) executing on host processors connected to the data network. In a packet network such as the Internet a host processor encapsulates data from an application into data packets to send the data over the packet network. When a host processor receives the data packet from the packet network, the host processor unencapsulates the packets to obtain the data. The host processor then provides the data to the appropriate application.
The process of encapsulating data into a packet involves adding information such as source and destination addresses to the data to facilitate transmission of the data over the packet network. Conventionally, the encapsulation process follows a particular packet data protocol. A typical protocol defines the structure of a packet such as the location of the source address and the destination address in the packet. A protocol also may define procedures for routing the packet over the network using those addresses. For example, the components in a data network may use the destination address to determine where to send the packet. The recipient application may use the source address to determine which application sent the packet.
Common protocols used in conjunction with the Internet include Internet protocol (“IP”), transmission control protocol (“TCP”), user datagram protocol (“UDP”) and Internet control message protocol (“ICMP”). In general, IP relates to controlling data transfer between host processors, TCP relates to establishing sessions to transfer data between applications, UDP provides a faster but less reliable data transfer mechanism than TCP, and ICMP relates to error messages and network traffic statistics.
Data transmitted over public networks such as the Internet may be encrypted to prevent unauthorized parties from intercepting the data. Typically, a device connected to the network encrypts data using a cipher algorithm and an encryption key. The device sends the encrypted data over the network to another device that decrypts the data using the cipher algorithm and a decryption key.
Several standards have been developed to facilitate secure data transmission over data networks. For example, the Internet security protocol (“IPsec”) may be used to establish secure host-to-host pipes and virtual private networks over the Internet. IPsec defines a set of specifications for cryptographic encryption and authentication. IPsec also supports several algorithms for key exchange, including an Internet Key Exchange (“IKE”) algorithm for establishing keys for secure sessions established between applications.
Some systems include dedicated devices that offload some of the processing operations from the host processor. For example, a network processor may be used to perform some of the packet processing operations. A cryptographic accelerator may be used to perform the cipher algorithms to offload encryption/decryption processing from the host processor.
In a typical system, the primary data flow is from the host processor to the network processor then to the network, and vice-versa. In addition, the network processor routes packets that will be encrypted or decrypted to the cryptographic accelerator. The cryptographic accelerator then routes the encrypted or decrypted packets back to the network processor. In personal computer-based systems, the host processor, network processor and cryptographic accelerator typically are connected via a peripheral component interface (“PCI”) bus.
There is a perpetual need for increased operating speed and implementation flexibility in data communications systems. On the one hand, developers are continually creating applications that require increasingly greater amounts of data to be sent between system components. On the other hand, end users want their applications to run faster which, in turn, often requires that associated data transfers be performed more quickly.
In an attempt to address the need for faster data communications, various groups have developed standards that specify high-speed data transfers between components of data communication systems. For example IEEE standards 802.3ab and 802.3z define Ethernet systems for transferring data at rates up to one gigabit per second (1 Gbit/s). IEEE standard 802.3ae defines an Ethernet system for transferring data at rates up to 10 Gbits/s.
The development of these standards and the ever increasing need for faster data transfers create a need for techniques and circuits capable of achieving high data transfer rates. Moreover, there is an ever-present economic motivation to achieve such results in a cost effective and adaptable manner. Accordingly, a need exists for improved packet processing techniques to support data transmission over data networks.